1. Field of the Invention
The present invention relates to a decomposition treatment liquid for a cured unsaturated polyester resin, a method for treating a cured unsaturated polyester resin by the use of the treatment liquid, and a method for separating a composite material.
2. Description of the Related Art
Cured polyester resins are excellent in thermal resistance, mechanical properties, weather resistance, chemical resistance, water resistance and the like, and therefore, the resins are utilized in various fields.
However, since unsaturated polyester resins are thermosetting resins, they do not melt after molded and further are insoluble in general-purpose solvents, so that it is difficult to reuse them. Moreover, various fillers to be mixed for improving mechanical properties and the like are difficult to dissolve, and hence, these materials cannot be reused.
As inventions aiming at the separation of a filler from a cured resin, a method for thermally decomposing the resin at a temperature of 900xc2x0 C. or higher is known for separating and recovering silica from a molded material, as disclosed in Japanese Patent Application Laid-Open Nos. 1993-139715 and 1994-87123. Additionally in Japanese Patent Application Laid-Open No. 1995-330946, there is also disclosed a method for recovering the filler by the thermal decomposition of a thermosetting resin.
In these inventions, however, since the resin is thermally decomposed to gasify it, the decomposed product of the resin cannot be reused except for its reuse as energy. Moreover, since a high temperature of 300xc2x0 C. or higher is usually required for decomposing the resin, there is a possibility that fillers other than silica are degraded to make their reuse impossible. Moreover, for the thermal decomposition at a high temperature exceeding 300xc2x0 C., there is required a special apparatus for controlling the reaction temperature and pressure. Furthermore, special attention for safety is needed owing to the operation at a high temperature and a high pressure.
As a method for the thermal decomposition of an unsaturated polyester, Japanese Patent Application Laid-Open No. 1996-85736 discloses a method for the thermal decomposition together with a feed source of a hydroxyl group. According to the publication, the temperature necessary for the thermal decomposition is generally in a range of from 370 to 390xc2x0 C. Moreover, the publication describes xe2x80x9cAt the thermal decomposition of the resin, the resin is preferably heated at a temperature range of from about 340 to 900xc2x0 C., particularly about 350 to 450xc2x0 C.xe2x80x9d.
However, the thermal decomposition at a high temperature exceeding 300xc2x0 C. requires a special apparatus for controlling the reaction temperature and pressure. Moreover, special attention for safety is needed owing to the operation at a high temperature and a high pressure.
On the other hand, as a method of the decomposition at a lower temperature as compared with the case of the thermal decomposition, there is a method of chemical decomposition. As a method for chemically decomposing an unsaturated polyester resin, Japanese Patent Application Laid-Open No. 1996-113619 discloses a method of using a base and a hydrophilic solvent. Japanese Patent Application Laid-Open No. 1996-134340 discloses a method of using a base and a monohydric alcohol. Moreover, a method of using a glycol is disclosed in Japanese Patent Application Laid-Open No. 1996-225635 and a method of using a dicarboxylic acid or a diamine is disclosed in Japanese Patent Application Laid-Open No. 1997-221565. Japanese Patent Application Laid-Open No. 1997-316311 discloses a method of using diethanolamine.
However, since these methods employ corrosive chemical substances, special attention toward the human body and the environment is indispensable. Moreover, in the case of using no corrosive chemical substance, the method is not practical because of an extremely slow decomposition rate.
In the case of decomposing or dissolving a cured unsaturated polyester resin for the purpose of reuse the raw materials, it is generally not preferable to decompose the resin thermally.
In general, in the thermal decomposition under an atmosphere containing oxygen, carbon atom and hydrogen atom are oxidized to form carbon dioxide and water, respectively, and therefore, it is difficult to used them as synthetic raw materials of a resin.
Furthermore, in the thermal decomposition under an atmosphere containing no oxygen, hydrogen atom bonded to carbon atom is liable to be eliminated, whereby mainly carbon is formed. Therefore, it is difficult to reuse it as a raw material of a resin.
Further, in the case of separating the decomposition product of a cured unsaturated polyester resin from a filler for the purpose of reusing each of them, it is difficult to reuse them because melting, oxidization, or a change of crystalline structure of the resin occurs and thereby, changes of strength and form thereof are resulted in when the filler is excessively heated.
Moreover, the methods of using corrosive chemical substances are not preferable in view of harmfulness to the human body and necessity of special consideration for safety of the apparatus.
Furthermore, in view of the efficiency at dissolution, higher decomposition rate or dissolution rate of the cured resin is more preferable.
An object of the invention is to decompose or dissolve efficiently a cured unsaturated polyester resin which is used for small crafts, automobile parts, railroad vehicle parts, furniture, bathtubs, electrical appliance, water-reservoir tanks, and the like.
Moreover, another object of the present invention is to separate efficiently a filler from decomposed components of a cured unsaturated polyester resin.
The present invention includes a decomposition treatment liquid for cured unsaturated polyester resins, comprising a phosphoric acid-type compound or salt thereof, and an organic solvent.
The salt of phosphoric acid-type compound preferably includes potassium phosphate, more preferably potassium phosphate hydrate.
The treatment liquid may contain an alkali metal ion.
The treatment liquid may contain an alcohol-based solvent or an organic solvent having a boiling point of 170xc2x0 C. or higher. Preferably, the treatment liquid is an alcohol-based solvent having a boiling point of 170xc2x0 C. or higher.
The present invention also includes a method for treating a cured unsaturated polyester resin comprising a step of decomposing or dissolving the cured unsaturated polyester resin using the above treatment liquid.
At the treatment, the temperature of the treatment liquid may be 250xc2x0 C. or lower. Moreover, the resin may be treated under atmospheric pressure.
The present invention also includes a method for separating a composite material containing a filler and a cured unsaturated polyester resin wherein the composite material is separated into the filler and a cured resin powder or a solution of decomposed product of the cured resin by treating the cured resin with the above treatment liquid.
According to the treatment liquid of the present invention, a cured unsaturated polyester resin can be easily decomposed or dissolved.
Moreover, according to the invention, a cured unsaturated polyester resin can be converted to a reusable resin material by decomposition or dissolution thereof.
Furthermore, according to the present invention, by decomposing or dissolving a cured unsaturated polyester resin using a specific treatment liquid, a composite material containing a filler and a cured unsaturated polyester resin can be separated into the filler and the resin, each of which can be easily reused.
Namely, the present invention is effective for reuse of a molding which comprises using a cured unsaturated polyester resin.
The present disclosure relates to subject matter contained in Japanese Patent Application No. 2000-390804, filed on Dec. 22, 2000, the disclosure of which is expressly incorporated herein by reference in its entirety.